Filtering scattered light in microchip-based cell diagnostics

A major challenge for light scattering techniques is the ability to simultaneously collect data over a wide angular range. This is of particular interest if light scattering is used for medical diagnostics of biological cells. The intricate relationship between scattered light and cellular morphological structure is especially visible over the whole scattering regime. Unfortunately, intensity levels of the scattered light display large variations over scattering angles. Consequently, low and high angles of scattering cannot be concomitantly imaged in one single test. Repeated measurements over a series of angles are time consuming and inefficient. On the other hand, preferential sampling of only a few scattering angles results in overlooking important information contained in other angular ranges. We propose the use of an interference filter for selective attenuation of scattered light. Our approach is to employ a commercial shortwave-pass filter. We discuss how to obtain adequate contrast between scattering peaks to enable detection over a wide angular range. The filter is incorporated into the design of a microchip-based optical device for single cell medical diagnostics. It is expected that this inexpensive device will provide advantages arising from simultaneous imaging of a wider angular range.